The locking and unlocking devices to which the disclosure applies are commonly referred to as locks, grippers, or jammers in the ship's chandler field.
For hoisting and setting the sail(s) of a sailboat, it is necessary to use various ropes (in particular halyards and sheets) that, depending on the operation, slacken (ease), or tension (trim) said sail(s) to which they are connected. Beyond a certain wind speed and also depending on the surface area of the sails, the force to be exerted on the ropes requires mechanical assistance to be used, in particular via devices for locking and unlocking said ropes. Depending on the size of the sailboat and on the weather conditions, tensions of several hundreds of kilograms (kg) and even up to two metric tonnes are exerted on the ropes.
Devices for locking and unlocking elongate tubular elements, such as ropes, are usually mechanical devices, each of which has a rigid or semi-rigid main part that is machined or molded. Such a main part preferably has a cylindrical through hollow inner portion passing the rope to be locked and unlocked. Such a device also has mechanical means that are manually actuatable for locking and unlocking the rope in said hollow portion, it being possible for such means to be a lever, a spring system or indeed crenellated or serrated portions that, in any event, flatten the rope over a portion of its length in order to lock it. Said flattened portion thus goes from being substantially circular in cross-section to being oval and flattened in cross-section.
Such devices suffer from numerous drawbacks. Since the rope is locked by being flattened, it sometimes tends to slip inside said inner portion, thereby changing the setting of the sails. In addition, since the rope is flattened, and subjected to difficult wear conditions (salt water, sun, etc.), the mechanical flattening accelerates mechanical and chemical degradation of the rope.
Such mechanical devices are not suitable for ropes that are merely braids, because such ropes slip and cannot be locked reliably. It is thus necessary to provide a braided over-sleeve or a covering in order to improve the behavior of the rope and thus in order to enable it to be locked reliably.
Even when over-sleeves or coverings are provided over the ropes, certain high-performance materials, such as, for example, ultra high molecular weight polyethylene (marketed, for example, under the Dyneema® trademark), when they are disposed on the outside of the rope, make it impossible for such ropes to be locked effectively because the ropes then slip in such mechanical devices because of the very low coefficient of friction of said materials.
Such mechanical devices are individually limited to very specific outside diameters for the ropes because it is necessary to match the outside diameter of the rope to be locked and the inside diameter of the hollow inner portion in a manner that is suitable for obtaining effective locking.
When such mechanical devices are unlocked, the tension is often released suddenly so that it is then necessary to re-tension the ropes. To mitigate that drawback, prior to the unlocking, a free portion of the rope is mounted on a winch, thereby making it possible, while the rope is being unlocked, to re-tension the rope as it is being released.
Document WO 91/02179 discloses a locking device comprising a housing from which an actuating arm projects that is coupled to a locking sleeve that, in its internal volume, receives an elongate element to be locked. By means of the actuating arm, the user causes the compression exerted by the locking sleeve on said element to vary by moving two portions of the locking sleeve towards each other or apart from each other. That device is designed, in particular, to be fastened to the deck of a boat. That housing is voluminous, complex to manufacture, and affords little possibility for improving the slippage resistance that is imparted by the locking sleeve. Increasing the tenacity and the weight of the yarns used in the clamping sleeve is limited by the available internal volume. In addition, that locking sleeve is manufactured from wires that, in operation, act abrasively on the surface of the elongate element, in particular in the boating field, in which half the ropes sold are made of multi-filament yarns of polyethylene terephthalate (PET).
The device disclosed in Document U.S. Pat. No. 4,055,875 suffers from the same drawbacks as mentioned above because of the presence of a housing having a limited internal volume. In addition, the means for locking the elongate element are not formed by a braided locking sleeve, as in the device of the preceding document, but rather they are made up of one or more strands coiled around the elongate element to be locked. It can be understood that the slippage resistance that is imparted is low, in particular since that locking device is adapted for the climbing field, i.e. for withstanding a maximum of a few hundred kilograms.
There therefore exists a need, in particular in the boating field, for a locking and unlocking device that is compact, easy to adjust and to implement, inexpensive, and that makes it possible to achieve high locking strength (also referred to as slippage resistance in the remainder of the present text).